1. Field of the Invention
The present invention relates to a clamp. In particular, but not exclusively, the invention relates to a down-thrust clamp for clamping a workpiece to a machine tool, or for clamping a workpiece in a jig or a mould.
2. Discussion of the Known Art
An example of a down-thrust clamp is that sold by Halder Norm+Technik under the model number 2331. This clamp has a clamping jaw that can be swung through 360.degree. to allow the workpiece to be changed. The clamp is applied by means of a handle that has an eccentric cam, which bears on the upper surface of the clamping jaw.
The clamp described above has the disadvantage that in order to apply the clamp, two separate movements are required: first the clamping jaw has to be swung into position above the workpiece, the position being determined by the user and is not automatically repeatable, and second, the handle has to be pressed downwards to bring the clamping jaw into clamping engagement with the workpiece. This can be very time consuming if a large number of clamps are being used. Further, the stroke of the clamp is rather limited, with the result that variations in the thickness of the workpiece cannot easily be accommodated.
If the clamp is incorrectly adjusted with the result that the eccentric cam reaches the end of its travel, this might give the impression that the clamp is fully applied when, in fact, it is not. This might lead to a risk of the workpiece becoming loose during a machining operation.